Removable cable cards, which provide proprietary decryption functionality for received TV audio and video, have been provided to enable consumers to purchase TV receivers such as set-top boxes in one cable provider area, then use them in another cable provider area should the consumer move there or otherwise wish to use the receiver there. In essence, instead of having to buy an entire new set-top box when a consumer moves from one cable provider area to another, which otherwise is necessary to be able to decrypt TV programming using the typically proprietary encryption scheme of the cable provider, the user need only acquire a new and relatively less expensive cable card. Thus, cable cards are removably engageable with TV receivers to provide the necessary decryption functionality, and each cable provider can lease cable cards with its own proprietary encryption scheme to consumers who move into that provider's area. The remainder of the set-top box or other TV receiver advantageously remains useful in all cable provider areas because the remaining components of the receiver typically are not proprietary.
Recent trends have provided receivers that support not just conventional one-way communication from the TV signal head end to the receiver, but also two-way communication, to support so-called “interactive digital video”. Examples of interactive digital video include pay-per-view, in which a TV receiver user can input certain requests and commands, as well as purchase orders, for pay-per-view programming using the TV receiver, and video-on-demand, entailing many of the same communication considerations. Also, so-called “switched digital” can be implemented using two-way TV receivers. Switched digital in essence allows all the viewers in a particular area to in essence report back to the head end what channel they are viewing, so that, for instance, the head end may take intelligent steps with respect to bandwidth such as ceasing transmission into the area of a channel that is not currently being viewed by anyone in the area and thereby releasing bandwidth for other uses.
Partly to support such two-way interactive digital video, the Open Cable Application Platform (OCAP) has been introduced. In effect, OCAP defines an application platform interface implemented by the TV receiver platform which allows software applications, downloaded to the receiver, to communicate with the receiver through a common standard interface and exploit its functionality. In turn, the OCAP interface communicates through the receiver's communication port with the TV signal head end. In this way, for example, viewer purchases of video-on-demand may be facilitated, with the purchased video then transmitted from the head end to the receiver, to be decrypted by the cable card of the receiver and then displayed on the TV screen.
As understood herein, the use of OCAP can entail rather expensive hardware requirements, and some consumers may not desire the added OCAP functionality and instead prefer a less expensive receiver. As also understood herein, in such receivers it would be desirable to allow third parties to provide applications that do not rely on OCAP, to support certain functionalities such as certain graphical user interfaces for the TV including cross-media bars, etc.
The present invention further recognizes, however, that each cable provider, in addition to implementing its own proprietary encryption scheme, also typically employs a proprietary application protocol from the TV receiver back to the head end. With this understanding in mind, the present invention recognizes that the cable card may have further use, in addition to decrypting incoming video, in also transforming outgoing messages from the third party applications in the receiver (which do not necessarily know the cable provider's proprietary application protocol to the head end) into messages that are understandable by the head end.